1. Field of the Invention
The present invention relates to a laminated electronic component and a method for manufacturing the same. In particular, the present invention relates to a laminated electronic component in which external terminal electrodes connected to internal conductors are formed on outer surfaces of an electronic component main body through a direct plating step and a method for manufacturing the same.
2. Description of the Related Art
In recent years, the market for small portable electronic equipment, e.g., cellular phones, notebook personal computers, digital cameras, and digital audio equipment, has been increasing. In the portable electronic equipment, miniaturization has been advanced which, at the same time, performance has been improved. A plurality of laminated electronic components are mounted on the portable electronic equipment, and miniaturization and performance enhancement of these laminated electronic components have also been required. For example, miniaturization and an increase in capacity are required for laminated ceramic capacitors.
To achieve the miniaturization and increase the capacity of the laminated ceramic capacitor, it is useful to reduce the thickness of a ceramic layer. Recently, a capacitor in which the thickness of ceramic layer is about 3 μm or less has been used. At present, further reductions in thickness are required. However, there is a problem in that as the thickness of the ceramic layer is reduced, short-circuiting between internal electrodes readily occurs and, thereby, it is difficult to ensure quality.
It is also effective to increase an effective area of the internal electrode. However, in mass production of the laminated ceramic capacitor, it is necessary to provide a side margin between an internal electrode and a side surface of a ceramic element assembly and an end margin between the internal electrode and the end surface of the ceramic element assembly due to deviations in lamination and deviations in cutting of the ceramic green sheets. Therefore, when an increase in the effective area of the internal electrode is desired, it is necessary that the area of the ceramic layer is increased in order to provide a predetermined margin. However, there is a limit to the amount of increase in the area of the ceramic layer within the bounds of a dimensional standard of the product. Furthermore, the thickness of the external terminal electrode prevent an increase in the area of the ceramic layer.
Previously, the external terminal electrode of the laminated ceramic capacitor is formed by applying an electrically conductive paste to an end portion of a ceramic element assembly and baking the ceramic element assembly. As the method for applying the electrically conductive paste, a method in which the end portion of the ceramic element assembly is immersed in a paste bath and is removed therefrom is conventionally used. However, in this method, the electrically conductive paste tends to predominantly adhere to a center portion of the end surface of the ceramic element assembly due to the influence of the viscosity of the electrically conductive paste. Consequently, the external terminal electrode becomes thick at portions thereof (specifically, greater than 30 μm, for example), and the area of the ceramic layer has to be reduced accordingly.
Under the circumstances, a method has been proposed in which an external terminal electrode is formed by direct plating. According to this method, a plating film is deposited while an exposed portion of an internal electrode exposed at an end surface of a ceramic element assembly functions as a seed, and exposed portions of adjacent internal electrodes are connected to each other through growth of the plating film. According to this method, a thin, flat electrode film can be formed as compared to that formed by using the electrically conductive paste according to a method of the related art (see, for example, International Patent Publication WO 2007/049456).
However, when the external terminal electrode is formed through direct plating on an outer surface of the electronic component main body (ceramic element assembly), since the thickness of the plating film is relatively small, an intrusion path of moisture and other contaminants from the outside becomes short and, thereby, there is a problem in that the reliability in moisture-resistance at high temperatures is deteriorated.